An in-situ method is disclosed for removing contaminants from surface and near-surface soil by imposing a vacuum on the soil beneath a impermeable flexible sheet and then heating the soil with an electric surface heater that is positioned on the soil surface under the sheet. The heater is permeable to vapors which emanate from the soil when heated. A permeable mat, which may also be a good thermal insulator, separates the heater from the impermeable sheet and provides a conduit for flow of vapors to openings in the sheet. The openings, in turn, are connected to a vacuum manifold for collection of the vapors. A vacuum pump evacuates the region under the impermeable sheet such that the sheet, mat, and heater are pressed firmly against the soil surface by atomospheric pressure. The soil contaminants are removed by vaporization, steam distillation, and/or thermal decomposition.